I recently purchased a Lee “Big Stopper” filter. This is a 4×4″ solid neutral density glass filter that delivers 10 stops of light reduction power. In other words, it’s like putting a piece of welder’s glass in front of your camera. Solid ND filters are used to permit long exposures in otherwise bright conditions. Why would you want to do this?
In the right conditions, long exposures deliver a creative look that can make your images stand out. This technique can be a creative boost when you’re photographing popular places. In order for long exposures to work, you need both good equipment and the right conditions.
Long Exposure Essentials
Depending on the ambient lighting conditions and how slow you want your exposure to be, you’ll need a multi-stop solid neutral-density filter. Singh-Ray makes 10 and 5-stop screw-in filters, while the Lee filter is square and requires a 4″ filter holder and adapter ring. Singh-Ray also makes variable neutral density filters with adjustable strength. You definitely will need a solid tripod and head to support your camera. I recommend using a remote release, too. If the exposure is longer than 30 seconds (which will easily happen in overcast or twilight conditions), you’ll need to use the bulb mode via manual exposure on your camera and lock the shutter open with a locking remote release. I use a Nikon MC-30 remote release most of the time; it’s small and easy to pack.
When things start getting dark, like when you put a 10-stop filter in front of your lens, your camera meter may not be able to calculate a proper exposure. I recommend using manual exposure mode, setting your aperture (usually f/11 or f/16) and then seeing what the “normal” exposure would be without the ND filter. Then, take the metered shutter speed and calculate the exposure based on the number of stops your filter adds. The proper shutter speed is calculated by multiplying your base exposure (without filter) by 2^x, where “x” is the number of stops of your ND filter.
- Base exposure without filter: 1/125s
- ND filtration: 10 stops
- 1/125x* 2^10 = 8.192 ~ 8 second exposure
Of course, this isn’t something that one often wants to do in their head, so it’s helpful if you have a calculator handy. Even better is a dedicated long-exposure smartphone App, like NDTimer (for iOS). This handy calculator makes it easy to figure out your exposure in the field. You simply set the unfiltered shutter speed and then dial in the amount of filtration that you’re using and it gives you the result.
Depending on conditions, sometimes your exposure will need to be more than 30 seconds long. If this happens, the only way you can time the exposure properly is to use the bulb exposure setting on your camera and use a timer or locking remote. Some high-end remote releases have built-in timers, like the Nikon MC-36. The other option is to use a manually locking remote cable and a timer or stopwatch. The ND Timer app I mentioned has a built-in timer function that automatically kicks in once exposures exceed 30 seconds. It’s super-easy to use and beeps when the time expires.
The Right Conditions
The whole idea of long exposure photography is to create unique effects by blurring motion. Clouds and water are usually the best subjects for long exposures, as they can create soft foregrounds and skies with unique textures. Keep in mind that your subject is going to have to be quite stationary otherwise it will become blurred, too. I like to use a relatively wide focal length to get “cloud trails” in the sky. If your shot does not contain some kind of moving object, then you won’t get an interesting effect no matter how long the exposure is.
Capturing the softness of moving water and clouds is fun, but you can also use long-exposure photography to remove otherwise distracting elements from your scene. Anyone who’s been to a popular tourist spot knows that it can be impossible to get a photograph without people in it. However, if you have a solid ND filter and the conditions are right, you might be able to get shutter speeds of several minutes. In these conditions, anyone in the shot who doesn’t stand still for a really long time will just disappear completely. That’s an interesting way of creating the illusion of a vacant landmark on an otherwise busy day!
My good friend and colleague, Deborah Sandidge, has set up a Facebook Group dedicated to long exposure photography. It’s a great place to get inspired and share your own photos!